DATA FLOW DIAGRAM

DATA FLOW DIAGRAM

- Data Flow Diagram (DFD) is a graphic illustration of the system that uses a number of forms of symbols to describe how data flows through a process of inter-related. Despite the name this diagram emphasizes the data, the situation is vice versa: the emphasis is on the process.

- Some symbols used in the DFD to represent:

1. External entity

2. Data Flow

3. Process

4. Data Storage

CONTEXT DIAGRAM

- The diagram which consists of a process and describe the scope of a system.

- It is the highest level of the DFD that describes the entire system to input and output of the system

- The system is limited by Boundary (depicted by broken lines)

- No storage

ZERO DIAGRAM

- Diagram illustrating the process of the DFD. Giving views on the overall system in which, showing the main function or process that is, the flow of data and external entity.

- At this level of data storage is possible.

- To process the detailed no longer on the next level then added the symbol '*' or 'P' at the end of the process.

- Input and output balance (balancing) between 0 to diagram context diagram should be maintained.

DETAIL DIAGRAM

- Is a diagram of the process of decipher what is in the zero diagram level or above.

- Numbering of level at DFD:

Level Name	Diagram Name	Number of Process
0	Context
1	Diagram 0	1.0, 2.0, 3.0, ...
2	Diagram 1.0	1.1, 1.2, 1.3, ...
3	Diagram 1.1	1.1.1, 1.1.2, ...

- In the one level there should be no more than 7 units and the maximum of 9, when more should be done in the decomposition.

SPECIFICATION PROCESS

- Each process in the DFD must have a specification process.

- At the top level method is used to describe the process you can use with descriptive sentences.

- At a more detailed level, namely on the bottom (functional primitive) require a more structured specification.

- Specification process will be the guideline for the programmer to make this program (coding).

- Method used in the specification process: the process of disintegration in the form of a story, decision table, decision tree.

EXTERNAL ENTITY

- Something that is outside the system that will provide data to the system or providing data from the system.

- Symbol with the notation.

- Unity does not include the outside of the system

DATA FLOW

- Flow data consist of a group of related data elements in a logical move from one process to another process.

- Depicted with a straight line connecting the components of the system.

- Flow data is shown with the direction arrows and the name on the flow of data that flows.

- Cash flow of data between processes, saving data, the unit outside, and shows data flow from data in the form of inputs to the system.

- Guidelines of the name:

1. Name of the flow of data that consists of some words associated with the flow lines connect.

2. No flow data for the same and the name should reflect its content

3. The flow of data that consists of several elements can be expressed with the group element

4. Avoid using the word 'data' and 'information' to give a name to the flow of data

5. Wherever possible the complete flow of data is written

6. Name of the flow of data into a process may not be the same as the name of the data flow out of the process

7. Data flow into or out of data storage does not need to be given a name if:
- Flow of data simple and easy to understand
- Flow of data describes all data items

8. There can be no flow of data from the terminal to the data storage, or vice versa because the terminal is not part of the system, the relationship with the terminal data storage must be through the process.

PROCESS

- The process is to change the input into output. The process can symbolize with a circle or tetragon with this degree obtuse angles.

- The transform function of one or more of data input into one or more of the output data in accordance with the desired specifications.

- Each process has one or more inputs and produce one or several outputs.

- Each process must be given a full explanation include:

1. Identification process, namely the form of a figure that shows the reference number of the process and is written at the top.

2. Name of the process, that is what the show is done by the process.

3. Processing

DATA STORAGE

- Storage of data is the data that have savings in the system.

- Savings symbolize data with a pair of parallel lines or two lines with one of the side open.

- Guidelines of the name:

1. The name should reflect the data storage

2. When his name more than one word must be marked with the number

DATA DICTIONARY

- Working to help the system to interpret the application in detail and organize all elements of the data used in the system precisely so that the system analyst and have a basic understanding of the same input, output, storage and processing.

- At analysis, the data dictionary is used as a means of communication between the systems analyst with the user.

- At the design stage of the system, the data dictionary is used to design input, reports and databases

- Flow data on the global DAD, further details can be seen in the data dictionary

- Load the data dictionary as follows:

1. Name of data flow: must note that readers who need further explanation about a flow of data can find it easily

2. Alias: alias or other name of the data can be written if support.

3. Forms of data: used to segment the data dictionary to use when designing the system

4. Flow data: indicates from which data flows and where the data

5. Description: to give an explanation of the meaning of the data flow

BALANCING IN DFD

- Flow of data into and out of a process must be the same as the flow of data into and out of the details of the process on the level or levels below

- The flow of data into and out of the process must match the name of the flow of data into and out of the details of the process

- Number and name of an entity outside the process must be equal to the number of names and entities outside of the details of the process

- The issues that must be considered in the DFD which have more than one level:

1. There must be a balance between input and output of one level and next level

2. Balance between level 0 and level 1 at the input or output of stream data to or from the terminal on level 0, while the balance between level 1 and level 2 is seen on the input or output of stream data to or from the process concerned

3. Name of the flow of data, data storage and terminals at each level must be the same if the same with this object.

RESTRICTIONS IN DFD

- Data flow may not be from outside the entity directly to other outside entities without going through a process.

- Data flow may not be from the savings directly to the data to outside entities without going through a process

- Data flow may not be saving the data directly from the savings and other data without going through a process.

- Data flow from one process directly to the other without going through the process of saving data or should be avoided as much as possible.

REFERENCE:

- Slide Kuliah : Diagram Aliran Data. NGURAH AGUS SANJAYA ER, S.KOM, M.KOM

- McLeod, Raymond. Sistem Informasi Manajemen Jilid 1